My Gerbil weaves it's head, sort of bobs it, squints, and/or stands up on hind legs and wobbles it's head from side to side.

*If the gerbil is a red-eyed one, this is not unusual. The red or pink eye is lacking pigments and this can cause things to literally be too bright for it. The weaving and bobbing is because of that. This almost always is confined to a pink or red eyed gerbil

I have a gerbil that is a tan (or grey) (or cream) and/or has the genes LLYyMmTg....

*I'm sorry, I don't do genetics. To me it's an alphabet soup with so many variations that I'm confused. Same with trying to figure out a color. For colors or gene predictors, a good start point I've found is the American Gerbil Society's 'color strip' chart. They have a nice little cross reference list to help you sort out what color your animal might be, and have some pictures of from first fuzz to full fur to first moult to mature animal of each color. Julian Barker of the National Gerbil Society is an expert at the alphabet soup. Several others have excellent websites and links about the same. Start with www.agsgerbils.org or www.gerbils.co.uk (AGS and NGS/GML)

I have ants in my tank or cage!

*Ants are drawn to food and water. Putting the tank or cage on a table at least 3" (8cm) away from any walls, drapes, or adjoining furniture, then putting the legs of the table into soup cans and putting a ring of white petrolium jelly (vaseline) at least 1" wide (3cm) inside or outside the can top will give a barrier. If you are cleaning the cage weekly and removing uneaten fresh food within a few hours, this should not be a problem unless you have an ant infestation. In which case, try to isolate the tank or cage from the ants, then use some means to rid your domicle of the ants. IF you have an aquarium instead of a cage, you can put the ring of white petrolium on the outside of the tank about 1" below the top.

My gerbil(s) insist on jumping for the top of their cage or tank repeatedly. Bang bang bang bang bang...

*I find that bored gerbils will do this. Or if there is something irritating them, such as bedding they're allergic to. Or spoiled rotten gerbils that find doing it gets them attention and/or you taking them out. Or if there are squabbles or dominance issues going on.

Bored gerbils... if it's not a breeding pair, give them an exercise wheel. You may have to give them one for each animal. The wheels are better if they're slung from the top of the tank, they're less likely to be jammed up then with burrowing in the bedding attempts. Or, more cardboard to chew up....

If an animal is allergic to the bedding (not uncommon) they will often try to escape to elsewhere, especially right after the tank is cleaned. Look for puffed fur or discharge from eyes/nose, and respiratory problems.

If there's one being bullied or losing the dominance fights they will try to escape to elsewhere to get away from their tormentor.

Some are spoiled to wanting to be out of the cage all the time and will spring as soon as you show up, demanding to get out, and keep it up. Seems to work as sooner or later you come over and open the cage and let them out (an arm to run up or you pick them up).

Then there are those adventurous spirits that Just Want Out. They may be batchelor boys and smell the females in heat next door, or smell the ladies on you because you just handled them...and go crazy.

In solo animals, the leaping is definitely boredom, and possibly an indication the animal will take to a friend introduced by splitcage over a few weeks.

"Lethal Genes" or "Missing Genes"???

The known lethal gene is the Spotted Gene. Written Sp. If an animal has none, it's sp. This is a dominant gene, so if an animal has one Sp they will show spotting. Even very light or white animals may carry the Sp gene...or otherwise the Sp gene will mask other color traits and make identification of the animal difficult.

IF a gerbil embryo gets Sp from both parents, it is lethal, and the embryo will not develop, being resorbed in the womb. It doesn't hurt the mother and you have no idea that you even had a SpSp happen.

The odds if you breed an Spsp to an Spsp (both showing spotting) for getting SpSp pups is 1:4 FOR EACH PUP. Or, 1:4 you get spsp (no spotting), 2:4 Spsp (spotted) and 1:4 SpSp (or lethal). If the female ovulated eight times, EACH EMBRYO runs the same chance. You may find that you don't seem to get pups, or compared to the rest of the breeder pairs you have the litters seem smaller...but most likely you will have the usual size litters. Don't plan on breeding Sp to Sp to give you small litters as a means of birth control. You will be up to your eyeballs in pups most likely.

As for 'missing' genes, this is such a rare occurance that the odds are one in millions. This would happen during the separation of the DNA helix during formation of the egg or sperm.. as in an incomplete or clumpy separation...or during the fusing of the two strands back into one helix during fertilization. Again, this is so rare that you can't expect to see it ever. If it did happen, most likely the embryo would not be viable and be resorbed by the female.